Mold on attic hatch 5 months after moving in

Hello everyone, we moved into our new build (bungalow) in September last year. Now, after only 5 months, we have discovered mold on the retractable floor stairs or hatch. The roof is a cold roof. The hatch is wet on the side facing the roof and the veneer is slightly peeling off there - mold is visible underneath.

We are now a bit uncertain about how to proceed.

a) How can mold occur here? Do we have to live with this in the case of a cold roof and arrange some kind of insulation ourselves?
b) Do we need to hire an expert to find out the cause, or should we contact the house building company directly?
c) Does anyone have any idea what can be done against the mold here? It really annoys me that we have such issues after such a short time.

If anyone knows anything, we would be very grateful for help.

Best regards, Susann

The hatch probably does not close properly, warm air is drawn through and condenses on the hatch. Your first point of contact is the [Hausbaufirma].

The hatch presumably does not close properly, warm air is drawn in and condenses on the hatch.

your first contact is the home construction company.

Thanks. Then we will report it there.

One more question about that: Shouldn't this have actually been detected during the Blower Door Test? I mean, that the hatch does not close properly?

Figuratively, the hatch would have had to open to fail the BD test, check if all the seals of the hatch are seated all around and are in place

Exactly. Perhaps the hatch is also not installed correctly and warm air is coming in from the side.

During our renovation, we noticed that the attic hatch to the cold attic had a few centimeters of "gap," which was concealed by paneling. However, no mold was found there. We then installed a properly closing and flush-fitted staircase.